Most modern day helicopters are high technology aircraft that incorporate a plethora of avionics/electronic modules that markedly improve the overall capabilities of the helicopter, enhance the flight operations thereof, and/or reduce the pilot/co-pilot workloads. As is well known, operation of these modules generates a large quantity of thermal energy that must be effectively dissipated, i.e., by cooling, to ensure continuous, reliable operation of the avionics/electronic modules. To dissipate such thermal energy, helicopters typically include an environmental control system (ECS) that provides a temperature/pressure regulated airflow for cooling of the avionics/electronic modules. The regulated airflow is generally further utilized for crew comfort, and may be used for over pressurizing the helicopter to preclude contaminant infiltration.
Military aircraft, especially helicopters, that are utilized for combat flight operations may be exposed to chemical, biological, and/or nuclear hazards. As a result, such aircraft are typically equipped with a nuclear/biological/chemical life support system (NBC LSS) to facilitate combat flight operations under such hazardous conditions. The NBC LSS ensures that NBC particulates/contaminants are removed from the airflow processed by the ECS.
System design engineers are continually striving to enhance the efficiency of helicopter subsystems while concomitantly reducing the complexity and weight thereof. To this end, the ECS and NBC LSS of helicopters have been combined into an integrated environmental control system. The integrated environmental control systems of modern day military helicopters typically combine the ECS and the NBC LSS functions into a single system that provides a decontaminated, cooled airflow for cooling of avionics/electronic modules and crew comfort.
Helicopter system design engineers continue to work to optimize the structural and functional characteristics of such integrated environmental control systems. Prior art NBC systems utilized low pressure carbon filters to remove NBC particulates/contaminants. Carbon filter NBC systems, however, initially proved inappropriate for helicopter applications. In order for the NBC system to perform effectively, the carbon filter, perforce, was too large and heavy for helicopter applications, system weight being one of the primary design constraints for helicopters, particularly military helicopters. The effectiveness of carbon filters was increased and the size thereof reduced by increasing the operating pressure of the carbon filter. Increasing the operating pressure of the integrated environmental control system, however, caused a concomitant increase in the weight of the airflow ducting of the integrated environmental control system.
Moreover, even though NBC particulates/contaminants may be effectively removed utilizing a high pressure carbon filter, such filters do not remove a sufficient amount of the moisture content of the cooled, decontaminated airflow to facilitate effective utilization of such airflow. Typically, the cooled, decontaminated airflow exiting the ECS portion of the integrated environmental control system must be channeled in parallel paths to the aircraft cockpit and avionics/electronic modules to achieve the desired cooling effects due to the moisture content thereof. If such cooled, decontaminated airflow is directly utilized for cooling of avionics/electronic modules, there is a risk that such airflow will induce moisture condensation and/or freezing in the avionics/electronic modules. To negate the possibility of such effects due to the moisture content of the cooled, decontaminated airflow, the cooled, decontaminated airflow is further conditioned, e.g., by mixing warmer airflow with such airflow or utilizing a heat exchange apparatus to raise the temperature of the airflow slightly above freezing (32.degree. F), prior to being utilized to cool the avionics/electronic modules.
The need to effect such downstream conditioning of the system airflow severely limits the overall efficiency of the integrated environmental control system. Firstly, the airflow cooling capacity of the ECS portion of the integrated environmental control system is not effectively utilized in light of the requirement for downstream conditioning, i.e., heating, of the cooling airflow. Secondly, the conditioned cooling airflow has a limited thermal cooling capacity that is essentially exhausted in cooling the avionics/electronic modules in mission equipment package bays. In light of this, the integrated environmental control system requires a second cooling airflow for the cockpit. The cooled, decontaminated airflow channeled directly to the cockpit, however, has a temperature that is generally too low for cockpit usage. Therefore, the cockpit cooling airflow is further conditioned by a heat exchange apparatus so as to raise the cockpit cooling airflow to a temperature that provides a comfortable cockpit environment. The components necessary to provide downstream conditioning of the cooled, decontaminated airflow, as well as the ducting required to provide parallel flowpaths of cooling airflow, and the size of such ducting in light of the reduced thermal cooling capacity of the conditioned airflow, increase the overall complexity and weight of prior art integrated environmental control systems.
It is known in the art to utilize a pressure swing adsorption (PSA) NBC filtration apparatus as part of an integrated environmental control system. A representative example of such a system is illustrated in U.S. Pat. No. 4,769,051. The PSA apparatus described in the '051 patent is operative not only to remove NBC particulates/contaminants from the generated airflow, but also to remove substantially all the moisture content thereof. That is, the PSA apparatus provides a super-dry, decontaminated airflow.
An examination of the integrated environmental control system described in the '051 patent, however, reveals that such system is not optimized for helicopter applications. The integrated environmental control system described in the '051 patent is a closed, two loop cooling system similar in structure and function to the closed, two loop cooling systems employed in nuclear reactors. A closed, two loop cooling system is not an optimum configuration for helicopter applications, requiring ancillary components and airflow ducting to effectuate the desired cooling function, which increases overall system weight, while concomitantly having a lower overall operating efficiency.
The cooled, super-dry, decontaminated airflow generated by the PSA apparatus and the air cycle machine described in the '051 patent is channeled through a first loop that passes through a load heat exchanger. A second loop, which includes the closed environment to be cooled, also passes through the load heat exchanger. The cooled, super-dry decontaminated airflow in the first loop is therefore utilized to indirectly cool the airflow of the second loop for subsequent cooling of the closed environment.
A need exists to provide an integrated environmental control system that has an improved operating efficiency and a lower overall system weight. The integrated environmental control system should provide a super-cooled, super-dry, decontaminated airflow and should be design optimized to fully utilize the thermal cooling capacity of the super-cooled, super-dry, decontaminated airflow for direct cooling of helicopter avionics/electronic modules and crew comfort.